ICON LVDC: Earthing and Protection Methodology for Non-Galvanically Isolated Low Voltage DC Grid
The anticipated shift toward decarbonization and the energy transition across all industrial sectors will demand extensive electrification. As fossil fuels and other energy sources are gradually phased out, reliance on electricity as the primary energy carrier will grow, making the continuous availability of electricity critically important. In this context, Low Voltage Direct Current (LVDC) systems are gaining popularity because they bring a range of advantages, particularly in energy efficiency, flexibility, and enabling the integration of multiple independent electricity sources, such as AC grids, photovoltaics, batteries, and fuel cells.
Achieving economic feasibility for LVDC integration at an industrial site remains challenging, particularly in ensuring effective protection when connecting to existing AC infrastructure. To this end, we aim to develop a novel protection method for ultra-reliable, industrial low voltage direct current (LVDC) systems at megawatt scale. The challenge is to enable effective protection without the need of galvanic isolation between the active and direct current systems, which is crucial for minimizing upfront investments, especially in existing brownfield installations. The protection method will rely upon the capabilities of novel protection devices to eliminate faults in a time range of ten μs (100 times faster than conventional technologies). The method will be developed, modeled and verified in a laboratory setting and, if successful, will result in a blueprint for industrial LVDC systems that could be applied to similar industrial sites, improving resilience and enabling service-to-grid at lower investment costs.
Low voltage direct current (LVDC) systems offer opportunities for industrial sites i) to locally increase availability of electricity towards critical users; ii) to integrate local energy resources and iii) to enable support of the AC grid. However, to make LVDC economically feasible for an industrial site, it should be integrated into existing AC infrastructure without a galvanic isolation transformer between both systems.
This project aims at facilitating the introduction of industrial LVDC grids with megawatt power rating and industrial applications through research on the safety and protection of non-galvanic isolated LVDC grids. The integrated earthing system between the AC and DC systems and the need for selective fault protection to ensure high availability, require research and design of a custom protection methodology using novel protection devices, such as solid-state circuit breakers, the general objective of the project.
The project will research five concrete objectives that will facilitate the introduction of non-galvanic isolated LVDC grids in the industry and to leverage research on those grids.
- Topologies for non-galvanic isolated LVDC grids
Topologies for non-galvanic isolated LVDC grids are crucial for grid operators, as these topologies comprise the converters, infeed, loads and earthing system possibilities and limitations which will allow choosing an application depending on its requirements.
2. Simulation models for non-galvanic isolated LVDC grids
Dynamic simulation models are required to research the fault behavior of non-galvanic isolated LVDC grids. However, these simulation models must be accurate enough to reflect the fault behavior but also compatible with general purpose personal computers with reasonable time efforts. Additionally, the simulation models need to reflect common-mode currents that may cause damage to assets in the investigated grids.
3. Method for calculating fault currents in non-galvanic isolated LVDC grids
For engineering LVDC grids, a method is needed to estimate fault-currents as these govern the dimensioning of cables, earthing system and protection method. Such fault current calculation method must be accurate enough to reflect the worst-case scenarios while remaining simple enough to limit the engineering effort.
4. Protection method for non-galvanic isolated LVDC grids
A protection method grants the safe and reliable operation of the non-galvanic isolated LVDC grid and is committed to interrupt fault currents within a few milliseconds to i) ensure human safety preventing electrocution during isolation faults; ii) selectively isolate faulty grid parts to allow or restore supply to the unharmed rest of the grid and iii) limit the asset damage. In addition, the method shall be robust, (i.e. immune to electrical disturbances in the grid and measurement inaccuracies) to avoid unwanted tripping that could impair system availability. The protection method will govern the selection of protective devices, such as breakers and the coordination between them during faults.
5. Quantitative benefits of a non-galvanic isolated LVDC grid
To motivate and enforce the adoption of non-galvanic isolated LVDC grids by the industry, the advantages of these grids must be measured to yield quantitative benefits, being i) efficiency that leads to reduced CO2-emissions and operational costs; ii) availability and reliability that prevents costly power outages and iii) potential for islanded operation that improves resilience against blackouts. Moreover, these grids may not cost excessive amounts of time to engineer them and common-mode currents must not pose a threat to the operation. The current project will addresses this objective using the methods from objectives 2 and 3 for a theoretical industrial use-case. Shortcomings will also be identified for future research.
Partners
The consortium consists of three industrial companies: ABB, BASF Antwerpen NV and DEP and EnergyVille/KU Leuven as research institute.
This project is supported by:
